Description (taken directly from the application): The goal of this program projects is to study the cellular and molecular biology of hematopoietic stem cells. To accomplish the goals of the program?s individual projects, it is straightforward that a reliable source of hematopoietic stem and progenitor cells is required. Also required are culture systems which allow for the storage, assay, and expansion of these cells. The goal of Stem/Progenitor Cell Core is to meet these needs by supplying the program?s investigators with well characterized murine and human hematopoietic cells from a variety of cellular sources and at various levels of differentiation. To support this goal the core has developed two specific aims which are as follows: 1) Optimize presently established methods for isolation and storage of human and murine stem/progenitor cells, and 2) Establish, and make available long and short term culture systems for bioassay of the developmental potential of isolated cells, including transplantation models into immunodeficient mice.